Understanding therapeutic change processes is important for the enhancement of therapeutic effectiveness, especially with change- resistant patients. Therapeutic interventions in which the therapist prescribes the very symptom the client seeks to change (i.e., "paradoxical interventions") are hypothesized to induce differential change sequences with patient who are inclined to defy the intervention and patients who are inclined to comply with it. Whereas the former utilize the mechanism of reactance to induce behavior change, the latter's compliance leads to a cognitive change (i.e., increased self- efficacy), which is expected to lead to behavior change. These interchangeable change mechanisms will be studied in proposed project. The role played by insomniac patients' reactance and perceived self- efficacy in mediating change process will be examine under two types of paradoxical and one type of non-paradoxical intervention conducted under controlled experimental conditions. Clients who meet DSM-IIIR criteria for primary insomnia will: (a) be further screened to ensure a clear differential diagnosis, and (b) undergo two sessions: the first takes place in a psychophysiology and sleep lab; the second takes place in a psychotherapy and psychophysiology lab. Clients' reactance is expected to interact with the type of treatment: the highly reactant is expected to interact with the type of treatment: the highly reactant will benefit more from paradoxical, whereas the low reactant will benefit more from the non-paradoxical treatment. The course of post-treatment change in reactant and non-reactant clients will be followed. A special focus of the post-treatment and follow-up examination will be on the role that perceived self-efficacy plays in maintaining and facilitating further therapeutic changes among the two subtypes of patient (reactant and non- reactant), within the different types of treatment. The current project represents a revision of a previous submission, the focus of which is the controlled examination of therapeutic change mechanisms. Assessment diagnosis, objective measures outcome (sleep latency), and additional measures of hypothesized mediating variables such as anticipatory anxiety and the meaning of the symptom. In accordance with these changes, we strengthened the therapeutic package and extended the period of post-treatment and follow-up assessment. Additionally, the construct of reactance is further explicated and developments in regards to its non-verbal measurement are detailed. Changes and additions are indicated by bold type.